JP2017204365A - Method for manufacturing solid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a solid battery which is improved in battery performance by preventing a short circuit in a battery element.SOLUTION: A method for manufacturing a solid battery comprises the steps of: applying a laser to a surface of an active material layer, which is a positive or negative electrode active material layer of a battery element having the positive electrode active material layer, a solid electrolyte layer and the negative electrode active material layer in this order, thereby causing the delamination of the active material layer and solid electrolyte layer at an interface thereof, provided that the laser has an intensity enough to cause the delamination at the interface of the active material layer and solid electrolyte layer; and removing the active material layer subjected to the delamination.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for manufacturing a solid state battery.

  A solid battery in which an electrolyte solution in a normal secondary battery is replaced with a solid electrolyte has attracted attention. The solid battery is attractive in that it does not cause decomposition of the electrolyte due to overcharging of the battery and has high cycle durability and energy density.

  The solid battery has a battery laminate in which a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and the like are laminated. For example, the battery laminate may be deformed by cutting or the like in a processing process, may be deformed by repeated charge / discharge, or may be partially damaged due to vibration during use. For example, the positive electrode active material layer and the negative electrode active material layer may contact each other and short-circuit. Therefore, regarding the battery laminate in the solid state battery, a shape and structure capable of suppressing a short circuit even when the above-described event occurs, and a manufacturing method thereof have been studied.

  For example, Patent Document 1 discloses a solid secondary including a step of forming a battery element that is a laminate of a positive electrode, a solid electrolyte, and a negative electrode on a current collector, and then cutting the battery element by means such as laser ablation. A battery manufacturing method is disclosed.

JP 2001-015153 A

  In the technique of Patent Document 1, the battery element is cut and divided by means such as laser ablation, and the effect of the short circuit of the divided battery stack in one region is exerted on the battery elements in other regions. It is intended not to be. However, according to studies by the present inventors, when a simple laser ablation method is applied to the removal of the active material layer, it may be difficult to remove the active material layer. Furthermore, this technique is not intended to fundamentally avoid short circuiting of the battery element itself.

  The present invention has been made in view of the above circumstances. Accordingly, an object of the present invention is to provide a method for manufacturing a solid state battery with improved battery performance by preventing a short circuit in the battery element.

The inventors have the following means:
A battery element having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer in this order on the surface of the active material layer that is a positive electrode active material layer or a negative electrode active material layer. Irradiating a laser having a strength that causes peeling at the interface to cause peeling at the interface between the active material layer and the solid electrolyte layer;
It has been found that the above object can be achieved by a method for producing a solid state battery, comprising a step of removing the active material layer from which the peeling has occurred.

  According to the present invention, a short circuit in the battery element is prevented, and a solid battery having improved battery performance can be manufactured by a simple method. The removal of the active material layer in the method for producing a solid battery of the present invention can remove the active material layer in the laser irradiation region without causing the active material around the removal region to rise.

FIG. 1A is a three-dimensional laser microscope image after removal of the active material layer by the laser ablation method. FIG.1 (b) is a conceptual diagram which shows the state of the cross section of Fig.1 (a) AA. FIG. 2A is a three-dimensional laser microscope image after the active material layer is removed by the method of this embodiment. FIG. 2B is a conceptual diagram showing a cross-sectional state taken along line AA in FIG. FIG. 3 is an SEM image, a three-dimensional laser microscope image, and a conceptual diagram showing how the active material layer is removed by the method of the present embodiment. FIG. 3A is a cross-sectional SEM image of the battery element before processing, and FIG. 3B is a state after the laser irradiation with the intensity that causes the active material layer to peel off at the interface with the solid electrolyte layer (upper stage). Is a perspective three-dimensional laser microscope image, the lower is a cross-sectional SEM image of the upper line AA, and FIG. A two-dimensional laser microscope image, the lower part is a conceptual diagram of a cross section taken along line AA in the upper part). FIGS. 4A to 4D are conceptual diagrams for explaining the manufacturing process of the electrode elements used in the examples and comparative examples. FIGS. 5A to 5F are perspective three-dimensional laser microscope images showing the surface state after removal of the positive electrode active material layer in the electrode elements in Examples and Comparative Examples.

  Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

<Removal of active material layer in this embodiment>
The solid battery manufacturing method of this embodiment includes a step of irradiating a surface of an active material layer of a battery element with a laser to cause peeling at an interface between the active material layer and the solid electrolyte layer, and the peeling occurs. Removing the active material layer. Said battery element is a laminated body which has a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer in this order, and the active material layer which this battery element has is a positive electrode active material layer or a negative electrode active material layer. The removal of the active material layer in this embodiment is shown in FIGS. 3A to 3C as an example in which the positive electrode active material layer is removed.

  The active material layer removed by the method of this embodiment may be either a positive electrode active material layer or a negative electrode active material layer. However, it is preferable to apply the active material layer removal step in the present embodiment as the positive electrode active material layer removal step from the viewpoint of more effectively expressing the effects of the present invention (FIG. 3A).

[Laser irradiation]
The energy of the laser applied to the active material layer is set to a strength at which the active material layer causes peeling at the interface with the solid electrolyte layer. The specific energy intensity can be easily known by a few preliminary experiments by those skilled in the art. That is, the active material layer surface of the electrical element to be irradiated is irradiated with a test beam with a specific energy intensity, and the state of the irradiated region is observed. The observation result confirms whether or not the energy intensity is appropriate. And an appropriate irradiation energy amount can be set by changing energy intensity as needed and performing test irradiation again.

  If the energy intensity of the laser is insufficient, peeling does not occur at the interface between the active material layer and the solid electrolyte layer in the irradiated region. If the energy intensity is appropriate, the active material layer in the irradiated region peels off at the interface with the solid electrolyte layer to form a void, but does not fall off from the battery element (FIG. 3B). If the energy intensity is excessive, a part of the active material layer in the irradiated region is removed by evaporation, but the exposed region of the solid electrolyte layer and the remaining region of the active material layer may be mixed in spots.

  Observation of the state after the laser test irradiation can be performed by, for example, cross-sectional observation using a scanning electron microscope (SEM) or surface shape observation using a three-dimensional laser microscope.

Specific examples of the energy intensity at the time of laser irradiation include a range of 360 mJ / mm ² or more and 570 mJ / mm ² or less.

  If the energy intensity of laser irradiation is within the above range, the effect of laser irradiation on the lower layer (for example, the solid electrolyte layer) can be minimized while expressing the desired effect of the present embodiment. At this time, it is also possible to further reduce the influence on the lower layer by dividing the energy in the appropriate range and performing pulse irradiation.

[Removal of active material layer]
In the present embodiment, the active material layer in the irradiated region where peeling has occurred at the interface with the solid electrolyte layer by the laser irradiation is removed to expose the solid electrolyte layer in the region (FIG. 3C). The removed active material layer can be removed by applying an appropriate physical force to the active material layer in the region. Examples of the physical force applied here include blow (for example, air blow) and additional laser irradiation.

  As described above, only the active material layer in a predetermined region can be selectively and completely removed from the electrode element, and the area between the positive electrode and the negative electrode after the electrode layer is removed by appropriately setting the laser irradiation region. The difference can be minimized. Therefore, the electrode element after removing the active material layer in a desired region by the method of the present embodiment is effectively prevented from being short-circuited between the positive and negative electrodes, and the energy density due to the area difference between the positive and negative electrodes. It is possible to provide a high-efficiency solid state battery in which the decrease in the temperature is minimized.

<Battery element and solid state battery in this embodiment>
Hereinafter, supplementary description will be given of the battery element suitably applied to the present embodiment and the solid battery obtained by using the electrode element from which the active material layer in a desired region has been removed according to the present embodiment.

[Battery element]
As a battery element manufacturing method suitably applied to the present embodiment, the following manufacturing method can be adopted:
(1) After applying an active material slurry (positive electrode active material slurry or negative electrode active material slurry) on the current collector layer, the active material layer (positive electrode active material layer or negative electrode active material) is dried or temporarily fired. Layer), and then applying a solid electrolyte slurry on the active material layer, and drying or baking the solid electrolyte slurry to obtain a solid electrolyte layer; a wet-on-dry manufacturing method;
(2) An active material slurry is applied to form an active material slurry layer, a solid electrolyte slurry is applied thereon to form a solid electrolyte slurry layer, and these are dried or fired to obtain an active material layer and a solid A wet-on-wet manufacturing method for obtaining an electrolyte layer; and (3) After individually drying or firing a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, the laminate is pressed. A manufacturing method using a laminated press system.

  The active material slurry used in the above method contains a positive electrode active material or a negative electrode active material and a solvent, and can further contain a binder, a conductive auxiliary agent, etc., and further contains a solid electrolyte described later. May be.

The positive electrode active material is not limited as long as it is a material used as a positive electrode active material of a lithium secondary battery. Specifically, for example, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), Li _{1 + x} Ni _1/3 Mn _1/3 Co _1/3 O ₂ (x is −0.05 or more and 0.50 or less. Lithium manganate (LiMn ₂ O ₄ ), Li _{1 + x} Mn _1-xy M _y O ₄ (M is one selected from Al, Mg, Co, Fe, Ni, and Zn) X is a number from 0.00 to 1.00, y is a number from 0.00 to 1.00), lithium titanate (Li _x TiO _y , x is 0.50) The number is from 2.00 to 2.00, and y is a number from 2.00 to 3.00.), Lithium metal phosphate (LiMPO ₄ , M is Fe, Mn, Co, or Ni), etc. Can be mentioned.

  As the negative electrode active material, other than carbon materials such as graphite and hard carbon; Si, Si alloy and the like can be used.

  As the binder, for example, butylene rubber (BR), polyvinylidene fluoride (PVdF), styrene-butadiene rubber (SBR), or the like can be used.

  As the conductive assistant, for example, carbon nanofiber (CNF), acetylene black (AB), ketjen black (KB), carbon nanotube (CNT) and the like can be used. As a commercial item of the CNF, for example, VGCF manufactured by Showa Denko KK is suitable.

  The solid electrolyte slurry used in the above method contains a solid electrolyte and a solvent, and preferably further contains a binder.

  Examples of the solid electrolyte include oxide-based amorphous solid electrolyte, sulfide-based amorphous solid electrolyte, halogen-based solid electrolyte, crystalline oxide or oxynitride-based solid electrolyte, glass ceramic-based solid electrolyte, and sulfide-based electrolyte A crystalline solid electrolyte or the like can be used.

Specific examples of these are as follows:
Examples of the oxide-based amorphous solid electrolyte include LiO ₂ —B ₂ O ₃ —P ₂ O ₅ and Li ₂ O—SiO ₂ ;
Examples of sulfide-based amorphous solid electrolytes include Li ₂ S—SiS ₂ , LiI—Li ₂ S—SiS ₂ , LiI—Li ₂ S—P ₂ S ₅ , LiI—Li ₂ S—P ₂ O ₅ , _{LiI-Li 3} PO ₄ and _{-P 2 S 5, Li 2 S} -P 2 O 5 and the like;
Examples of the halogen-based solid electrolyte include LiI and the like;
Examples of the crystalline oxide or oxynitride solid electrolyte include Li ₃ N, Li ₅ La ₃ Ta ₂ O ₁₂ , Li ₇ La ₃ Zr ₂ O ₁₂ , Li ₆ BaLa ₂ Ta ₂ O ₁₂ , and Li ₃ —PO. _{(4- (3/2) w)} N _w (w is a number greater than 0 and less than 1), Li _3.6 Si _0.6 P _0.4 O _{4 and the} like;
As a glass ceramic-based solid electrolyte, for _example, the _Li7P3S11, Li _{3.25 P 0.75} S _4, and the like;
Examples of sulfide-based crystalline solid electrolytes include Li _3.24 P _0.24 Ge _0.76 S ₄ ;
Each can be mentioned.

  The binder that can be contained in the solid electrolyte slurry is the same as that described above as the binder in the active material slurry.

[Solid battery]
The solid state battery according to the present embodiment is a known method or a method in which appropriate changes are made by those skilled in the art, except that the electrode element in which only the active material layer in a predetermined region is selectively removed by the above method is used. Can be manufactured. Such a solid battery of this embodiment has a high energy density with reduced risk of short circuit.

<Preparation of positive electrode laminate>
In a polypropylene container, butyl butyrate, a 5% by weight butyl butyrate solution of a polyvinylidene fluoride binder, LiNi _1/1/1/3 O ₂ (average particle size 4 μm) as a positive electrode active material, and LiI as a solid electrolyte Li ₂ S—P ₂ S ₅ series glass ceramics (average particle size 0.8 μm) and VGCF (trade name, carbon nanofibers manufactured by Showa Denko KK) as a conductive additive were prepared, and manufactured by SMT Co., Ltd. The mixture was stirred for 30 seconds using an ultrasonic dispersion apparatus “UH-50”. Next, the container was infiltrated for 3 minutes using a shaker “TTM-1” manufactured by Shibata Kagaku Co., Ltd., and then stirred for 30 seconds with the above-described ultrasonic dispersion device to prepare a positive electrode mixture.

  After shaking the positive electrode mixture for 3 minutes with a shaker, the positive electrode mixture is applied onto a release sheet (aluminum foil) by a blade method using an applicator and heated on a 100 ° C. hot plate. By drying for 30 minutes, a positive electrode laminate having a positive electrode active material layer on a release sheet was produced.

<Preparation of negative electrode laminate>
In a polypropylene container, butyl butyrate, a 5% by weight butyl butyrate solution of polyvinylidene fluoride binder, natural graphite carbon (Mitsubishi Chemical Corporation, average particle size 10 μm) as the negative electrode active material, and LiI as the solid electrolyte Li ₂ S—P ₂ S ₅ -based glass ceramics (average particle size 1.5 μm) was prepared, and stirred for 30 seconds using an ultrasonic dispersion device “UH-50” manufactured by SMT Co., Ltd. Next, the container was infiltrated for 3 minutes using a shaker “TTM-1” manufactured by Shibata Kagaku Co., Ltd., and then stirred for 30 minutes with the above ultrasonic dispersing device to prepare a negative electrode mixture.

  On the copper foil as a negative electrode collector, the said negative mix was apply | coated by the blade method using the applicator, and it was made to dry for 30 minutes on a 100 degreeC hotplate. The negative electrode mixture having the negative electrode active material layer on the negative electrode current collector layer was prepared by similarly coating and drying the negative electrode mixture on the opposite surface of the copper foil.

<Formation of solid electrolyte layer>
In a polypropylene container, butyl butyrate, a 5 mass% butyl butyrate solution of a polyvinylidene fluoride binder, and Li ₂ S—P ₂ S ₅ glass ceramics (average particle size 2.0 μm) containing LiI as a solid electrolyte. The mixture was stirred for 30 seconds using an ultrasonic dispersion apparatus “UH-50” manufactured by SMT Co., Ltd. Subsequently, the container was infiltrated for 30 minutes using a shaker “TTM-1” manufactured by Shibata Kagaku Co., Ltd. to prepare a solid electrolyte paste.

  On the release sheet (aluminum foil), the above-mentioned solid electrolyte paste is applied by a blade method using an applicator and dried on a hot plate at 100 ° C. for 30 minutes to have a solid electrolyte layer on the release sheet. A laminate (solid electrolyte laminate) was produced.

<Manufacture of electrode elements>
The solid electrolyte layer surface of the solid electrolyte laminate was laminated on both sides of the negative electrode laminate obtained above, and pressed at a pressure of 400 MPa (FIG. 4A). Thereafter, the release sheet on the solid electrolyte layer is peeled off to obtain a five-layer laminate in which the solid electrolyte layer, the negative electrode active material layer, the negative electrode current collector layer, the negative electrode active material layer, and the solid electrolyte layer are laminated in this order. It was.

  The solid electrolyte layer surface of the solid electrolyte laminate was further brought into contact with both surfaces of the five-layer laminate, and pressed at a pressure of 1400 MPa (FIG. 4B). Thereafter, the release sheet on the solid electrolyte layer is peeled off, and the solid electrolyte layer (two-layer body), the negative electrode active material layer, the negative electrode current collector layer, the negative electrode active material layer, and the solid electrolyte layer (two-layer body) A seven-layer laminate was sequentially laminated.

  The positive electrode active material layer surface of the positive electrode laminate obtained above was laminated on both surfaces of the seven-layer laminate, and pressed at a pressure of 400 MPa (FIG. 4C). Thereafter, the release sheet on the positive electrode active material layer is peeled off, whereby a positive electrode active material layer, a solid electrolyte layer (two-layer body), a negative electrode active material layer, a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer ( A two-layer body) and an electrode element that was a nine-layer stack body in which the positive electrode active material layers were stacked in this order were manufactured (FIG. 4D).

<Comparative Example 1>
Laser irradiation was performed on a part of the positive electrode active material layer surface of the electrode element with an irradiation energy of 330 mJ / mm ² , and then air blow was applied to the laser irradiation area as a physical force. However, this laser irradiation does not cause separation between the positive electrode active material layer in the irradiation region and the lower solid electrolyte layer, and therefore the positive electrode active material layer in the irradiation region cannot be removed even by applying physical force. There wasn't. It is thought that the laser irradiation energy is insufficient. A perspective three-dimensional laser microscope image after laser irradiation is shown in FIG.

<Examples 1-3 and Comparative Examples 2 and 3>
The positive electrode active material layer was removed in the same manner as in Comparative Example 1 except that the laser irradiation energy was set as shown in Table 1. The test results are shown in Table 1, and the perspective three-dimensional laser microscope images after the test are shown in FIGS.

As can be understood from Table 1 and FIGS. 5A to 5F, the laser is irradiated to cause separation between the active material layer and the solid electrolyte layer to completely remove the active material layer in the region. It was verified that the range of 360 mJmm ^{2 to} 570 mJ / mm ² is appropriate. When the irradiation energy was smaller than this range, for example, 330 mJ / mm ² , no peeling occurred in the active material layer in the irradiation region. On the other hand, when the irradiation energy is larger than this range, for example, 600 mJ / mm ² or more, the active material layer in the irradiation region cannot be completely removed, and a part of the active material layer remains.

  From the above results, the following can be understood.

  As the removal of the active material layer using laser irradiation, a laser ablation method can be considered. This method is a method of removing the active material layer in the laser irradiation region by heating it at once and vaporizing it. However, if this laser ablation method is simply applied to the removal of the active material layer as it is, the irradiation energy is weak in the peripheral part of the laser irradiation region, so that the active material layer in the peripheral part melts but does not vaporize. It seems to resolidify in a raised state. Further, a residue of the active material layer that does not evaporate remains in the region near the center of laser irradiation.

  FIG. 1 shows an example in which the positive electrode active material layer is removed in the above state. FIG. 1A is a three-dimensional laser microscope image after removal of the active material layer by the laser ablation method, and FIG. 1B is a conceptual diagram showing a cross-sectional state taken along line AA in FIG.

  The present invention provides a method for manufacturing a solid state battery, including a method for solving the problems in the simple application of the laser ablation method described above, and including a method for removing an active material layer in a laser irradiation region without bulging an end portion. Is.

  An example of the state after removing the positive electrode active material layer by the method of the above embodiment of the present invention is shown in FIG. FIG. 2A is a three-dimensional laser microscope image after the active material layer is removed by the method of this embodiment, and FIG. 2B is a conceptual diagram showing a cross-sectional state taken along line AA in FIG. is there. From FIG. 2, it is understood that the active material layer in the laser irradiation region can be completely removed without the rise of the end by the method of the present embodiment.

Claims (1)

A battery element having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer in this order on the surface of the active material layer that is a positive electrode active material layer or a negative electrode active material layer. Irradiating a laser having a strength that causes peeling at the interface to cause peeling at the interface between the active material layer and the solid electrolyte layer;
And a step of removing the active material layer from which the peeling has occurred.